Learning spinal manipulation skills: assessment of biomechanical parameters in a 5-year longitudinal study

Teaching spinal manipulation (SM) is a fundamental aspect of chiropractic training. Recent works have identified various biomechanical variables as indicators of SM performance and learning. However, only data from cross-sectional studies are available, limiting conclusions regarding the persistence of SM performance over the years. Therefore, the main objective of this investigation was to quantify the evolution of biomechanical parameters of SM over a 5-year learning period.

Thirty-three students enrolled in a chiropractic program participated in the present study. They were tested each year at the beginning of each fall semester by performing 10 SMs on an instrumented manikin while standing on a force plate. The procedure allowed us to measure various force-time parameters.

Overall, significant time effects were noted for most dependent variables. The results indicated rapid improvement in the peak force applied and the rate of force production during the first 2 years. Time to peak force decreased drastically during the first year, whereas preload forces reached satisfactory levels during the third year. When various force-time requirements of bimanual task components were met, learners significantly reduced trial-to-trial variability of SM peak and preload forces, indicating automaticity of performance. Although global coordination improved in all learning processes, it was only in the later phase that learners reached values approaching those of experts.

Overall, these results highlighted the importance of considering learning principles in the development of didactic strategies related to SM motor skills.